The present invention generally relates to apparatus in a architecture for converting variable frequency alternating current (AC) electrical power to controlled frequency AC electrical power, and, more specifically, to an apparatus for performing and controlling the AC-AC power conversion to supply power to aircraft systems.
An aircraft electrical architecture that uses electric power for engine starting, for the Environmental Control System (ECS), or to supply constant frequency to loads requires a number of components to perform the AC-DC and controlled DC-AC power conversion. The components required to perform the AC-DC power conversion, which may include components such as Transformer-Rectifiers or Auto-Transformers-Rectifiers (ATRU), together with the controlled DC-AC conversion components such as Inverters and the required contactors, add weight and complexity to the aircraft.
Weight is always at a premium in aircraft designs. Any reduction in weight is an important design consideration in aircraft systems and components. This is especially true in newer designs of unmanned aerial vehicles (UAV), where weight reduction is an important design consideration and carries considerable mission and performance enhancement. All aircraft designs benefit from any reduction in weight.
One prior art solution is disclosed in FIG. 1, which shows a conventional prior art AC-DC conversion circuit. A power supply circuit 100 includes an AC-DC conversion circuit 101 which includes several components. Three phase AC power supply 130 supplies power to an AC bus 135. The AC bus 135 distributes power to an AC/AC converter circuit 101 and starter/generator (S/G) 140. The AC-AC converter circuit 101 includes an AC-DC converter circuit 105 that converts input AC power to DC power. The AC-DC converter circuit 105 includes a rectifier (not shown) supplying rectified DC power to a high voltage DC (HVDC) bus 110 via a bank of capacitors (not shown) used as filters. The HVDC bus 110 is coupled to the AC-DC converter circuit 105 and used to distribute the output HVDC. The HVDC bus 110 couples to a DC-AC converter circuit 115, which converts the DC power to controllable frequency power. The different components are coupled using contactors 120 in the circuit. The AC-DC converter includes bulky Transformer-Rectifiers (TRs) (not shown) or Auto-Transformers-Rectifiers (ATRUs) (not shown). Bulky capacitors at the input of the inverters perform the filtering required for the AC/DC conversion. The TRs, ATRUs, and contactors add bulk, weight, and cost to the electrical circuit.
The switch 125 controls power flow to either a motor 145 or a starter/generator 140. In position B, the switch 125 connects power to the starter/generator 140 to allow high power flow for starter operation. When switch 125 is in position A, power from the starter/generator 140, when in generator operation, flows through the converter circuit 101 to provide power with controllable frequency to the motor 145.
Prior art attempts using diode fed converters to perform the AC conversion required DC link capacitors. These capacitors add weight and cost to the converter circuit and are heat sensitive.
Under current applications, an aircraft architecture that uses electric power for engine starting, for the Environmental Control System (ECS) or to supply constant frequency to loads requires a number of components to perform the AC/DC and controlled DC/AC power conversion adding weight, bulkiness, and cost to the overall aircraft design.
As can be seen, there is a need for an improved power architecture that performs power conversion to provide controlled variable frequency and constant frequency power at a reduced weight and cost compared to prior art systems. The controlled variable frequency delivered by the architecture is variable frequency controlled by the architecture.